Radiation therapy treatment of soft tissue tumors in the prostate using radiation therapy treatment is complicated by the proximity of the prostate to radiation-sensitive tissues. Radiation therapy treatment of the prostate is further complicated by prostate motion.
Typically, the planning of radiation therapy for the treatment of prostate cancer involves the patient undergoing a CT-based simulation scan of the pelvis to determine the location of the prostate gland. In the simulation procedure, the patient is placed on CT and/or MRI equipment that is similar to the radiation treatment equipment, except that it does not generate the high energy radiation beam. The simulation equipment is positioned to simulate the conditions experienced by the patient during delivery of the sequence of treatment beams prescribed by the treating oncologist. Normally, during the simulation procedure, CT and/or MRI images are acquired. These CT and/or MRI images allow the oncologist to locate the position of the tumor and develop a radiation treatment plan using a devoted radiation or proton therapy treatment plan. This treatment plan delineates the positions of the radiation equipment components for precise delivery of the radiation to a predetermined area.
During the subsequent treatment procedure, the patient is placed in the same position on the treatment equipment as in the simulation scans. Radiation-emitting devices are generally known and used for radiation therapy in the treatment of patients. During treatment, a radiation beam is delivered to the patient at the precise location as delineated by the physician during simulation. A further feature of radiation therapy involves portal images, which are commonly used to verify and record tumor location.
During external beam radiation, radiation is directed to the prostate, which is near the rectal wall. Rectal bleeding following radiotherapy is common, on the order of 20-30%, which translates into at least 10,000 men a year following treatment of prostate cancer. The cause of rectal bleeding following radiotherapy is overdosage of the rectum with radiation. The high incidence of rectal bleeding limits the total dose of radiation one can give the prostate cancer and therefore limits the potential cure rate for radiotherapy.
A large amount of attention has been directed to reducing the amount of rectal bleeding resulting from radiotherapy. One of the main ways physicians limit rectal bleeding is that they decrease the total radiation dose used to treat the patient's prostate cancer. However, this may lead to inadequate radiation treatment and a higher probability of local cancer recurrence. Another method physicians have used in an attempt to reduce rectal bleeding following radiotherapy is to use a daily balloon rectal catheter to immobilize the prostate. The most common and oldest balloon catheter methods use a balloon that inflates in the rectum behind the prostate. The mechanism of action is to force the posterior rectum away from the prostate. This mechanism of action is of very limited efficacy because the posterior rectum is rarely a cause of rectal bleeding. Of most concern for rectal bleeding is the anterior rectum that is directly adjacent to the posterior prostate.
More recent attempts at minimizing rectal bleeding using balloon catheters have been aimed at forcing the prostate into a fixed position to allow the radiation beam to be more precisely directed to the target tissue. The balloon catheter apparatuses disclosed in the prior art attempt to stabilize the prostate by using large-volume balloons (e.g. 100 cc or more) and, in some cases, have various protrusions that attempt to create a seating area to receive and immobilize the prostatic bulge. Large volume balloons and balloons with bulges distort the rectal mucosa to seat or “cup” the prostate. Large volume balloons also increase patient discomfort.
U.S. Pat. No. 5,476,095 and U.S. Patent Publication No. 2003/028097 both disclose a rectal balloon apparatus having an inner balloon and an outer balloon, and an overall balloon shape that is round with a saddle-shaped bulge on the anterior surface of the balloon. The inner balloon has an anterior section that is covered with an inelastic, adhesive backed cloth material. As the device is inflated, the inner balloon forces the anterior surface of the outer balloon against the prostatic region of the rectum. More specifically, as the balloon is inflated to approximately 60 cc, a saddle-shaped bulge receives the rectal prostatic bulge inferior to the ampulla of the rectum.
U.S. Patent Publication No. 2009/0221899 discloses a rectal balloon apparatus wherein the balloon element has two inflated conditions. The first inflated condition, occurring when approximately 100 cc of fluid are introduced into the balloon, creates a flat surface with a seating area for the prostate to rest. In the second inflated position, a bulbous portion protrudes from the balloon at a position adjacent to the tip of the balloon. This protrusion occurs when at least 140 cc of fluid are introduced into the balloon. The purpose of the bulbous portion is to better isolate the prostate.
The methods and balloon catheter apparatuses in the prior art have not adequately addressed the problem of rectal bleeding, as between 20-30% of men still experience rectal bleeding during radiation therapy treatments. Moreover, the use of large volume balloons and balloons with bulges that protrude into the anterior rectum to receive the prostatic bulge increase patient discomfort.